Happens, don’t worry about it. You can take some fiber supplements if it’s too much (it won’t break your fast).
Edit: also, if you are taking magnesium, try lowering the amount because it can cause diarrhea.
guessing too much salt . take some plain water. rest for a bit. lower potassium too it can make your heart rate change might be why you are dizzy. it you have access to a PB cuff take your PB. in the states you can buy them at Walmart or CVS…
If you get nauseous stop your fast . Gently. There is always another day to fast..